Gaming machines, such as slot machines, video poker machines and the like, have been a cornerstone of the gaming industry for several years. Generally, the popularity of such machines with players is dependent on the likelihood (or perceived likelihood) of winning money at the machine and the intrinsic entertainment value of the machine relative to other available gaming options. Where the available gaming options include a number of competing machines and the expectation of winning at each machine is roughly the same (or believed to be the same), players are likely to be attracted to the most entertaining and exciting machines. Shrewd operators consequently strive to employ the most entertaining and exciting machines, features, and enhancements available because such machines attract frequent play and hence increase profitability to the operator. Therefore, there is a continuing need for gaming machine manufacturers to continuously develop new games and improved gaming enhancements that will attract frequent play through enhanced entertainment value to the player.
One concept that has been successfully employed to enhance the entertainment value of a game is the concept of a “secondary” or “bonus” game that may be played in conjunction with a “basic” game. The bonus game may comprise any type of game, either similar to or completely different from the basic game, which is entered upon the occurrence of a selected event or outcome in the basic game. Generally, bonus games provide a greater expectation of winning than the basic game and may also be accompanied with more attractive or unusual video displays and/or audio. Bonus games may additionally award players with “progressive jackpot” awards that are funded, at least in part, by a percentage of coin-in from the gaming machine or a plurality of participating gaming machines. Because the bonus game concept offers tremendous advantages in player appeal and excitement relative to other known games, and because such games are attractive to both players and operators, there is a continuing need to develop gaming machines with new types of bonus games to satisfy the demands of players and operators.
Bonus games may be awarded as part of the outcome of the base game based on an expected value. The expected value for the bonus game remains constant and therefore events in the game do not have an effect on the probability of earning eligibility to play the bonus game. The random occurrence of bonus games may frustrate some players who have played the base game for long periods of time and expect some progress toward being eligible for the bonus game.
Thus, a need exists for a gaming system having a special event such as a bonus game whose expected value may be adjusted to reflect the unavailability of previous game enhancement parameters previously available to a player. There is a need for a gaming system that allows a special symbol to appear to signify a change in the probability of triggering a bonus event as part of a shift of expected value.